(1) Field of the Invention
This invention relates to gate drive voltage for magnetic memory technologies, such as Phase Change RAM and Spin Moment Transfer MRAM, sometimes referred to as Spin Torque Transfer MRAM, cells which require programming currents higher than the minimum cell transistor can provide without degrading the life of the cell transistor. More particularly the invention relates to circuits and methods for programming these cell transistors by applying high voltages between the gate and source or drain of the cell transistor only to those cell transistors into which a one or zero is being written.
(2) Description of Related Art
U.S. Pat. No. 7,046,547 B2 and U.S. Pat. No. 6,961,265 B2 to Witcraft et al. describe methods and apparatus that allow data to be stored in a magnetic memory cell, such as a giant magneto-resistance cell. The inventions describe advantageously winding a word line around a magnetic memory cell to increase the magnetic field induced by the word line.
U.S. Pat. No. 6,985,382 B2 to Fulkerson et al. describe a technique to read a stored state in a magneto-resistive random access memory device, MRAM, such as a giant magneto-resistance MRAM device or a tunneling magneto-resistance device, TMR. The technique uses a bit line that is segmented into a first portion and a second portion. An interface circuit compares the resistance of a first portion and a second portion of a first bit line to the resistance of a first portion and a second portion of a second bit line to determine the logical state of a cell in the first bit line.
U.S. Pat. No. 6,754,055 B2 to Ono et al. describes a giant magneto-resistive effect element which includes a laminated layer film having a ferromagnetic film, a non-magnetic film, and an anti-ferromagnetic film.
U.S. Pat. No. 6,714,390 B2 describes a giant magneto-resistive effect element capable of producing a high output and a high resistance and which can cope with a high recording density and a magneto-resistive effect type head, a thin film magnetic memory, and a thin film magnetic sensor each of which includes this giant magneto-resistive effect element.